Airborne Auxiliary Power Unit, abbreviated as APU, is a small turbine engine mounted at the tail of an aircraft. Its main function is to supply power and gas sources, with a few APUs capable of providing additive thrust to the aircraft. Specifically, before taking off from the ground, an aircraft may not need to rely on a ground power supply and gas source vehicle starting up it as its main engine may be started via the power supply from the APU. While on the ground, the APU also supplies power and compressed air to ensure lighting and air-conditioning in the cabin and cockpit. During take-off of an aircraft, the APU can serve as a backup power source. After the aircraft is landed, lighting and air-conditioning of the aircraft are still maintained by power from the APU. The functions of the APU determine that the operation stability of the APU directly affects the flight cost and quality of service of the aircraft.
Since the APU is a turbine engine, the turbine efficiency is an important parameter reflecting the performance of the APU. The prior art has no effective means for evaluating the turbine efficiency of an APU so that the performance of an APU cannot be evaluated. The present invention is to provide the means for solving this problem.